Additive Manufacturing Materials Science 211

3D

Three-dimensional. Having a length, depth, and width. 3D structures are created during additive manufacturing processes.

3D printing

The process of producing a 3D object using a specialized tool that creates successive layers of material. 3D printing must technically involve the use of a print head or nozzle, but the term is often used interchangeably with additive manufacturing (AM).

acrylonitrile butadiene styrene

ABS. A thermoplastic material with good heat, chemical, and impact resistance. Acrylonitrile butadiene styrene is a common polymer used in additive manufacturing processes.

additive manufacturing

AM. The process of joining or solidifying materials to make an object based on a three-dimensional computer model. Additive manufacturing methods typically build up layers of material to create an object.

additives

Any substance that is added to a material during manufacturing to improve its properties. Additives in plastics perform a range of functions, from changing the color to improving strength.

alloying elements

An element that is intentionally added to a metal to change its properties. Common alloying elements include chromium, manganese, nickel, and silicon.

aluminum

A lightweight metal that is silvery white in color. Aluminum resists corrosion and is a good conductor of electrical and thermal energy.

aluminum alloys

A metal containing aluminum, which is a silvery white metal that is soft, light, and has a high strength-to-weight ratio. Aluminum alloys are frequently used in automotive and aerospace applications because of their strength and light weight.

aluminum-silicon alloys

A metal containing larger amounts of aluminum and silicon along with various, lesser amounts of other alloying elements. Aluminum-silicon alloys are common types of aluminum alloys used in additive manufacturing processes.

aluminum-silicon-magnesium alloys

A metal containing larger amounts of aluminum, silicon, and magnesium along with various, lesser amounts of other alloying elements. Aluminum-silicon-magnesium alloys are common types of aluminum alloys used in additive manufacturing processes.

AM

Additive manufacturing. The process of joining or solidifying materials to make an object based on a three-dimensional computer model. AM methods typically build up layers of material to create an object.

amorphous regions

An area in a polymer where the molecules lack a definite repeating form, shape, or structure. Amorphous regions usually consist of large and complex molecule chains and branches.

amorphous thermoplastics

A molecular formation that lacks a definite repeating form, shape, or structure. Amorphous thermoplastics have a lower viscosity with increased temperatures.

annealing

The steady heating of a metal above the recrystallization phase, followed by gradual cooling. Annealing can reduce hardness, improve machinability, and facilitate cold working.

argon

A colorless, odorless type of inert gas. Argon is sometimes used in gas atomization processes and as a propellant in the metal spraying process.

atomic bonds

An attraction that forms when electrons are shared or transferred among atoms. Atomic bonds become the "glue" that holds the atoms together.

atomization

A group of processes that create powder by breaking up a liquid into very fine droplets. Atomization processes include water atomization and gas atomization.

atoms

The smallest unit of an element. Atoms bond together to form molecules.

binder jetting

An additive manufacturing process in which liquid binder is used to join powdered materials to create a part. Binder jetting systems use powdered plaster, metal, or sand.

biocompatibility

A material's ability to be used in living tissue without being toxic or causing injury. Biocompatibility is an important property for materials used in medical applications.

biocompatible

A material that can be used in living tissue without being toxic or causing injury. Biocompatible materials are frequently used to make medical implants.

biomedical

An industry that involves the application of both biology and medical sciences. Biomedical manufacturers often use additive manufacturing processes to build parts made from superalloys.

body-centered cubic

BCC. The metal crystal structure that contains an atom in the center and one atom in each corner of a cube. Body-centered cubic metals are often hard.

bond

An attraction that forms when electrons are shared or transferred among atoms. Bonds hold atoms together.

branched arrangement

A molecule chain with multiple branches or extensions of monomers. Branched arrangements of molecules can appear in both thermoplastics and thermosets.

brittle

A material's resistance to being drawn, stretched, or formed. Brittle materials can fracture when subjected to mechanical forces.

bronzes

Any copper-based alloy that does not use zinc or nickel as the primary alloying element. Bronzes commonly contain tin, aluminum, or silicon.

carbides

A chemical compound containing carbon and another element, such as chromium, tungsten, or titanium. Carbides are a type of ceramic.

carbon

A common, nonmetallic element that is combined with iron to create steel. Carbon content typically increases hardness in metal.

ceramic matrix composites

CMC. A composite made from an oxide, carbide, nitride, or boride matrix and reinforcement materials. Ceramic matrix composites are stiff, lightweight, and can withstand extremely high temperatures.

ceramics

An inorganic material that consists of both metallic and nonmetallic atoms held together by a strong primary bond. Ceramics include metal oxides, nitrides, and glasses.

char

To burn an object's surface until it becomes black or discolored. Charring of thermoset materials occurs when they are exposed to heat after their initial setting.

chemicals

Any substance, or mixture of substances. Chemicals may be in the form of solids, liquids, or gases, and may consist of an element such as hydrogen, or a combination of elements, such as water or saltwater.

chromium

A hard gray metal used in ferrous alloys to add hardness, hardenability, and wear resistance. Chromium is typically 15% of stainless steels.

cobalt

A shiny, silver-white metallic element. Cobalt is tough, brittle, and hard as well as highly magnetic.

cobalt-chromium-based superalloys

A superalloy containing larger amounts of cobalt and chromium along with various, lesser amounts of other alloying elements. Cobalt-chromium-based superalloys are common superalloys used in additive manufacturing processes.

coefficient of thermal expansion

The degree to which a material increases in size as temperatures increase. Coefficient of thermal expansion is an important material physical property.

composites

A material made by mixing two or more of the following groups: metals, polymers, and ceramics. Composite materials are categorized by their matrix material.

compound

A substance consisting of the atoms of two or more different elements in fixed proportions. Compounds can only be broken down by chemical processes.

compression strength

A material's ability to resist forces that attempt to squeeze or crush it. Compression strength is the amount of compressive stress a material can withstand before fracturing.

compressive stress

A force that attempts to flatten or squeeze a material. Compressive stress is a type of mechanical force.

cooling channels

A passage through which a cooling fluid is circulated to maintain a desired tool temperature. Cooling channels are sometimes referred to as cooling lines.

copper

A reddish nonferrous metal that is very ductile. Copper is thermally and electrically conductive as well as corrosion resistant.

copper alloys

A metal containing copper, which is a reddish metal that is very ductile, thermally and electrically conductive, and corrosion-resistant. Copper alloys include bronze and brass.

corrosion

The gradual deterioration of a material due to atmospheric exposure. Corrosion often appears on metal in the form of rust.

corrosion resistance

A material's ability to resist deterioration and chemical breakdown due to surface exposure in a particular environment. Corrosion resistance is an important physical property.

covalent bond

A chemical bond formed between atoms by the sharing of electron pairs. Covalent bonds are a strong type of primary bond that form in a thermoset during cross-linking.

cracks

A visible fracture or point of separation in the surface of a material. Cracks can originate from pores on the surface of additively manufactured metal parts and are a type of defect.

creep strength

A material's ability to withstand a constant force over an extended period or at elevated temperatures. Creep strength is a vital material property for superalloys used in aerospace and medical applications.

cross-linking

The formation of covalent bonds between polymer molecule chains. Cross-linking is a chemical reaction that occurs before a thermoset is manufactured.

cryogenic

The industry that deals with producing and using exceedingly low temperatures. Cryogenic industries often study the behavior of materials when exposed to temperatures below -292 degrees Fahrenheit, or -180 degrees Celsius.

crystal structures

The regular, repeating pattern of atoms in a material. Crystal structures in a metal develop as the metal drops below the recrystallization temperature and solidifies.

crystalline

A material consisting of crystals, which are formed by repeating patterns of atoms. Crystalline structures determine a material's unique properties and are found in both metals and ceramics.

crystalline regions

An area in a polymer where the molecules are packed together into regular, repeating patterns. Crystalline regions usually consist of small and simple molecule chains.

curing

The process of using heat, ultraviolet radiation, or pressure to harden a thermoset. Curing creates a chemical reaction that permanently cross-links the molecules.

damping

A material's ability to resist deformation through vibration. Damping capabilities in plastics are higher than the damping capabilities of metals.

defects

An imperfection in a part that prevents it from operating correctly. Defects sometimes appear in additively manufactured parts when layers do not adhere to each other correctly or when surface porosity occurs in a part.

deform

To change or distort an object's shape. Deformed objects have permanently lost their original shape.

density

The amount of mass within a specific volume. Objects with greater density increase in mass and weight.

die casting

A thermal, high-pressure metal casting process that involves injecting molten metal into a mold at high velocity and pressure. Die casting is a metal shaping process used in traditional manufacturing.

dies

A reusable mold that holds heated liquid metal and imparts its shape as the metal cools. Dies are made of two halves instead of being one solid object.

directed energy deposition

DED. An additive manufacturing process in which focused thermal energy is used to melt materials as they are deposited. Directed energy deposition is often used with powdered or wire metal.

ductile

A material's ability to be drawn, stretched, or formed without breaking. Ductile materials bend easily but resist fracture.

ductility

The measure of a material's ability to be drawn, stretched, or formed without fracturing. High ductility levels indicate a material can bend easily but resist fracture.

elastic

Possessing the ability to return to an original shape after having been stretched or deformed. Elastic materials include many different types of plastic.

elasticity

A material's ability to revert to its original shape after being stretched or compressed. Elasticity is a mechanical property.

electrical conductivity

The ability of a material to act as a medium for conveying electricity. Polymers often have low electrical conductivity, while most metals usually have high electrical conductivity.

electrical conductors

A material that allows free movement of electrons and therefore enables the easy flow of electricity. Electrical conductors are often metals.

electricity

A form of energy created by the movement of electrons. Electricity can be converted into light, heat, or motion.

electromagnets

A magnet formed from electric current. Electromagnets are typically formed by wrapping a current-carrying coil around an iron core.

electromechanical

To operate through a combination of electricity and mechanical motion. Electromechanical parts include relays, switches, and actuators.

electrons

A negatively charged particle that orbits the nucleus of an atom. Electrons are involved in chemical bonding and electrical conductivity.

end-use

Designed to be used directly by a consumer or directly in another manufactured product. End-use products created by additive manufacturing (AM) include medical implants, custom dental devices, and camera equipment.

epoxies

A thermoset polymer that is very tough and heat-resistant. Epoxies can be used in additive manufacturing processes.

face-centered cubic

FCC. The metal crystal structure that contains one atom in the center of the six sides of a cube and one atom in each corner of the cube. Face-centered cubic metals are often ductile.

fatigue resistance

A material's ability to resist failing due to repeated external stress. Fatigue resistance is an important material property for many applications.

ferrous metals

A metal in which iron is the main ingredient. Ferrous metals commonly used in additive manufacturing include different types of steel.

fibers

A slender, thread-like reinforcing material used in composites. Fibers are larger and longer than whiskers or particles.

filaments

An extremely thin strand of material. Filaments of thermoplastic material are used in some material extrusion additive manufacturing processes to build parts.

finishing process

The treatment of a surface to remove roughness and irregularities and improve its appearance. Finishing processes include sanding and painting.

firing

The heating of ceramic materials at elevated temperatures. Firing helps to solidify the material and improve its strength.

flammability

A material's characteristics that determine its ability or tendency to ignite or burn when exposed to an open flame. Flammability is one factor to consider during AM polymer selection.

fracture

To break apart into two or more pieces because of stress. Fracture is a type of catastrophic failure.

fuse

To blend with other materials to form a single object. Fused materials are joined together to form a final product in additive manufacturing methods.

gas atomization

An atomization process that creates powder by breaking up liquid into droplets using a high-pressure inert gas. Gas atomization produces uniformly shaped and sized powder particles.

glass transition temperature

The temperature at which a rigid solid becomes pliable and can be formed, shaped, or molded. The glass transition temperature of an amorphous thermoplastic is slightly below the melting point of a semicrystalline thermoplastic.

glasses

A transparent material made primarily from silica along with other ingredients. Glasses are a type of ceramic.

grades

A category, rank, or level of quality. Grades of steel are typically categorized by the specific amount of elements included in the steel.

graphites

A soft, black form of carbon. Graphites are a type of ceramic.

green sand

A material consisting of sand mixed with additives, such as clay, coal, and water. Green sand, which is the primary molding material for sand casting processes, is also called foundry sand.

grinding

A subtractive manufacturing process used to improve surface finish and bring parts into close tolerance. Grinding is often used to remove minor imperfections from a workpiece.

hardenability

A material's ability to be hardened by heat treatments or other processes. Steels have varying degrees of hardenability, depending on their alloying elements.

hardness

A material's ability to resist penetration, indentation, or scratching. Hard materials tend to be very strong and resistant to wear.

heat resistance

The ability to resist degradation when under extreme heat. Heat resistance is important for plastics that will be exposed to heat on a regular basis.

heat treatment

The controlled heating and cooling process used to change the structure of a material and alter its physical and mechanical properties. Annealing, quenching, and tempering are heat treatments.

helium

A light, colorless, nonflammable inert gas that is much lighter than air. Helium is sometimes used in gas atomization processes.

hexagonal close-packed

HCP. The metal crystal structure that contains a collection of atoms that are closely packed into the shape of a hexagon. Hexagonal close-packed metals are often brittle.

horizontally

Parallel to the horizon or ground. Horizontally oriented objects span from side to side or left to right.

hybrid material

A material made by combining two or more separate substances together. Hybrid materials exhibit properties and characteristics that are superior to those of each individual material.

impact toughness

A material's ability to absorb energy from a sudden, sharp blow without fracturing. Impact toughness is also known as impact strength.

implants

An object that is inserted within an individual's body, usually through surgery. Implants must be made of materials that are biocompatible and will not cause a negative reaction within the body.

impurity

The degree to which a material contains foreign elements or substances. The impurity of a metal powder depends on its atomization process.

Inconel

A superalloy based in nickel and chromium that is designed to perform well in extreme environments. Inconel resists both oxidation and corrosion.

index of refraction

A measurement of the amount of and the speed with which light can pass through an object. The index of refraction for a material indicates its reflectiveness.

inert gas

A gas that does not chemically react with the substance it contacts. Inert gases include nitrogen, helium, and argon.

injection molding

A molding process in which liquid resin is heated in a barrel and deposited into a mold by a reciprocating screw. Injection molding is a metal shaping process used in traditional manufacturing.

inorganic

A material that does not contain carbon. Inorganic materials are derived from nonliving substances such as minerals.

insulators

A material or element that has little electrical conductivity and high resistance to electrical charges. Most insulators are plastics and ceramics.

ionic bonds

A type of atomic bond that occurs when one atom borrows one or more electrons from another atom. Ionic bonds are relatively strong.

iron

A silver-white, metallic element that is highly magnetic. Iron is alloyed with carbon to make steel.

linear arrangement

A molecule chain that consists of a long, flexible, chain of monomers that connect end-to-end with each other. Linear arrangements occur in straight-chain polymers.

liquid

A state of matter that is cohesive and can flow. Liquids are the room temperature forms of some substances, such as water, or the melted form of others, such as metals.

machining

A subtractive manufacturing process that involves removing material to form an object. Machining includes methods such as milling, turning, and drilling that remove metal using cutting tools.

macromolecules

A large molecule that consists of repeating molecular units. Polymers consist of long chains of multiple macromolecules.

magnetic fields

The area in and around a magnet in which a magnetic force exists. Magnetic fields exhibit the powers of attraction and repulsion.

magnetism

The power of attraction and repulsion that exists in some materials. Magnetism occurs more frequently between metals than polymers.

manganese

A hard, brittle, gray-white metal. Manganese increases strength and hardness in alloy steel.

maraging steels

A grouping of low-carbon steels that exhibit exceedingly high levels of strength, toughness, hardenability, and wear resistance. Maraging steels typically contain high levels of nickel along with cobalt, molybdenum, and titanium.

master patterns

A replica of a part or casting that is used to create a negative impression in a mold. Master patterns for molding and casting processes are traditionally made of plastic, wood, or metal.

material data sheets

Manufacturer-provided documents that describe a material's chemical composition as well as its mechanical and physical properties. Material data sheets include details such as a material's density, tensile and yield strength, hardness, and surface roughness.

material extrusion

An additive manufacturing process that uses a nozzle to dispense material, usually a thermoplastic filament, onto a support. One example of material extrusion is the fused deposition modeling (FDM) process.

material jetting

An additive manufacturing process in which droplets of build material are selectively deposited onto a build platform. Material jetting systems use a photopolymer that is cured by ultraviolet light.

matrix

The viscous material that binds together the reinforcing fibers of a composite and hardens to give the part shape and protect the fibers from damage. Matrix materials can be a variety of polymers, metals, or ceramics.

mechanical forces

A force that attempts to bend, stretch, break, or indent a material. Mechanical forces include compressive, shear, and tensile forces.

mechanical properties

The collection of properties that describe a material's ability to compress, stretch, bend, scratch, dent, or break. Mechanical properties of a material are determined by its molecular structure.

melting point

The temperature at which a material changes from a solid to a liquid. Melting points for semicrystalline materials are sharply defined, while amorphous thermoplastics have a glass transition temperature.

mer units

A single unit of atoms that chemically bonds to other similar units to form long, repeating polymer molecule chains. Mer units are also called monomers.

metal matrix composites

MMC. A composite made from a metallic matrix and high-performance reinforcement materials. Metal matrix composites have high levels of strength, stiffness, and relatively high resistance to heat.

metal oxides

A chemical compound containing oxygen and metal. Metal oxides, which include aluminum oxides and iron oxides, are a type of ceramic.

metallic bond

A type of primary atomic bond that occurs when atoms share electrons that float about in a general electron cloud. Metallic bonds are weaker than the other types of primary bonds, ionic and covalent bonds.

metals

A naturally occurring material group that consists of tightly packed atoms held together by a strong primary bond. Metals include copper, iron, nickel, and lead.

mixture

A substance consisting of two or more separate substances that are mixed, but not chemically bonded, together. Mixtures include the different types of composites.

moisture resistance

A material's ability to resist absorbing and becoming wet when exposed to water. Moisture resistance is one factor to consider during AM polymer selection.

molding

A process that involves pouring a liquid material into a closed mold to form a shape once it cools and solidifies. Molding is a traditional manufacturing process.

molecular structure

The arrangement of a molecule's atomic bonds and location of its atoms. A material's molecular structure is determined by the types of atomic bonds present as well as which atoms are bonded to other atoms.

molecular weight

The mass of a molecule. High molecular weight is a characteristic of thermoplastic molecules.

molecules

A group of atoms held together by either primary or secondary bonds. Molecules are the smallest unit into which a material can be divided without changing its properties.

molybdenum

A hard, silvery white metal used in metal alloys. Molybdenum can add toughness, creep strength, and wear resistance to steel.

monomers

A single unit of atoms that chemically bonds to other similar units to form long, repeating polymer molecule chains. Monomers are also called mer units.

natural polymers

A polymer that occurs in nature and is not synthesized by humans. Natural, or organic, polymers include amber, wool, and silk.

nickel

A silvery metal that is both tough and corrosion-resistant. Nickel is often added to metals as an alloying element.

nickel-based superalloys

A superalloy containing larger amounts of nickel along with various, lesser amounts of other alloying elements. Nickel-based superalloys are common superalloys used in additive manufacturing processes.

niobium

A ductile, metallic element that is used as an alloying element. Niobium is found in some superalloys.

nitrides

A chemical compound containing nitrogen, an inert gas. Nitrides are a type of ceramic.

nitrogen

A naturally occurring, colorless, odorless gas that can promote strength and resistance to pitting in stainless steels. Nitrogen is sometimes used as an alloying element or in different processes such as metal spraying or gas atomization.

nonferrous alloys

A mixture of two or more metals that does not contain iron as the main element. Nonferrous alloys commonly used in additive manufacturing processes include aluminum alloys, titanium alloys, and copper alloys.

nuclear power

An industry that involves producing energy using atomic reactions. Nuclear power applications often require the use of specialized materials such as superalloys.

nylon

A semicrystalline thermoplastic that gains strength when the fibers are stretched. Nylon is a commonly used term for polyamides (PA).

opacity

The lack of transparency in a material or the degree to which it absorbs light. Opacity is an optical property present in many polymers.

optical properties

An aspect of an object's physical appearance. Optical properties include a material's transparency, opacity, color, and index of refraction.

oxidation

A material's chemical reaction with oxygen. Oxidation can result in polymer degradation.

particles

A very tiny piece of material used as a reinforcement. Particles are smaller than whiskers or fibers.

pellets

A very small, round ball of material. Pellets of thermoplastic material are used in some material extrusion additive manufacturing processes to build parts.

photopolymers

A thermoset polymer that cures and hardens when exposed to light. Photopolymers are used in material jetting and vat photopolymerization systems.

physical properties

A set of characteristics that describes how a material responds to environmental, thermal, electrical, and magnetic forces. Physical properties describe how a material reacts to forces other than mechanical forces.

pliable

To be flexible and easily bent. Pliable materials are easily shaped.

pole

Opposite ends of an axis. Poles also refer to the opposite ends of a magnet.

polyamide

PA. A semicrystalline thermoplastic that gains strength when the fibers are stretched. Polyamides are commonly referred to as nylon.

polycarbonate

PC. A type of thermoplastic that is used for items that require high heat resistance. Polycarbonate is a common polymer used in additive manufacturing processes.

polycrystalline

Having a collection of multiple crystal grain structures with different orientations. Polycrystalline materials include most metals and ceramics.

polyethylene

PE. A polymer that has good ductility and impact strength. Some proprietary thermosets are designed to mimic the properties of polyethylenes.

polyimides

PI. A thermoset polymer that is lightweight and has good heat and chemical resistance. Polyimides can be used in additive manufacturing processes.

polymer matrix composites

PMC. A composite made from a polymer resin matrix and reinforcement materials. Polymer matrix composites are not as strong or heat-resistant as metal matrix and ceramic matrix composites.

polymers

A natural or synthetic material group that consists of very large molecules held together by either a secondary bond or a primary bond. Polymers include silk, nylon, rayon, and plastics.

polypropylene

PP. A polymer that is tough, flexible, and resistant to fatigue. Some proprietary thermosets are designed to mimic the properties of polypropylenes.

polyurethanes

PU. A thermoset polymer that is versatile and wear-resistant. Polyurethanes can be used in additive manufacturing processes.

powder bed

The area of a powder-based additive manufacturing machine that holds granulated construction material and provides the build platform. Powder beds are used in additive manufacturing systems, including binder jetting, selective laser sintering (SLS), and direct metal laser sintering (DMLS).

powder bed fusion

An additive manufacturing process that uses adhesives, heat, or light to bond areas in a container of powdered plastic, metal, ceramic, or other material. Powder bed fusion may use a variety of different channel configurations.

precipitates

Solid elements that have been separated from a type of liquid solution. Precipitates that separate out of a solution can change a metal's properties.

precipitation hardening

The process of heating an element to a temperature at which it precipitates and then cooling it at a rate to prevent return to the original structure. Precipitation hardening forms a harder structure.

pressure

A measurement of the amount of force exerted on a surface divided by the area of the surface. Pressure is typically expressed in pounds per square inch (psi).

primary bond

A bond between atoms that involves the exchanging or sharing of electrons. Primary bonds form strong connections within a material's molecules.

properties

The physical and mechanical characteristics of a material that distinguish it from other materials. The properties of a material can be altered with additives.

proprietary

Designed by a specific company for use only with its own systems. Proprietary materials include many polymers and superalloys that have been designed for specific applications.

prototypes

A preliminary model of a product used to evaluate the performance of a design. Prototypes provide a design basis for final products.

quenching

The soaking of a metal at a high temperature above the recrystallization phase, followed by rapid cooling due to exposure to a quenching medium, such as water, saltwater, air, and oil. Quenching can increase a material's hardness.

radiation

Energy emitted in the form of particles or waves. Prolonged radiation exposure can damage some materials.

reactive metals

A type of metal that undergoes a chemical reaction when combined with elements such as oxygen, hydrogen, or nitrogen. Reactive metals include titanium, nickel, and magnesium.

reactive sites

A specific portion of a polymer monomer chain that engineers create to allow for a chemical reaction between two or more substances. Reactive sites are necessary for cross-linking to occur in a thermoset.

recrystallization temperature

The temperature at which new grains are formed in a metal. Every metal has a specific recrystallization temperature.

reinforcement

The part of the composite that provides strength, stiffness, and the ability to carry a load. Reinforcement materials can be in the form of whiskers, particles, or fibers.

resin

A raw polymer, usually in the form of liquid, beads, or pellets, that is not yet molded into its final shape. Resin is melted to form plastic parts.

rigidity

The measure of a material's ability to resist bending or stretching. Rigidity is characterized by being stiff and inflexible.

rupture strength

A material's ability to resist permanent deformation or breakage after supporting a load over time. Rupture strength is a vital material property for superalloys used in aerospace and medical applications.

scalpels

A small and extremely sharp knife that is used by a surgeon during surgery. Scalpels are usually made of corrosion-resistant material, like stainless steel.

secondary bonds

A bond that involves attraction between molecules but no transferring or sharing of electrons. Secondary bonds are not as strong as primary bonds.

secondary shaping process

A shaping operation that occurs after plastic has already been formed or molded. Secondary shaping processes are sometimes used with thermoplastics.

semicrystalline thermoplastics

A thermoplastic with both amorphous and crystalline regions of molecules. Semicrystalline thermoplastics are melted at higher temperatures than amorphous thermoplastics because more heat is needed to encourage molecular movement.

shaping processes

The process of changing the shape of a piece of plastic. Shaping processes include molding, extrusion, and casting.

shear strength

A material's ability to resist forces that attempt to cause the internal structure to slide against itself and separate. Shear strength is the amount of shear force a material can withstand before fracturing.

sheet lamination

An additive manufacturing process that forms an object by bonding sheets of material together using an adhesive, heat, and pressure. Sheet lamination includes methods such as laminated object manufacturing and ultrasonic consolidation that are increasingly common in manufacturing operations.

softness

A material's ability to be scratched, indented, or penetrated by another material. Softness is the absence of hardness.

solid

A basic non-flowing form of a substance. Solids are the room temperature forms of some substances, such as aluminum, or the frozen forms of others, such as water.

spherical

To have a round, three-dimensional circular, or globular shape. Spherical metal powders are produced using the gas atomization process.

stainless steels

A grouping of steels that contain large percentages of chromium, as well as nickel, manganese, and/or nitrogen. Stainless steels have very high hardness and corrosion resistance.

steels

A type of metal consisting of iron and carbon, usually with small amounts of other elements. Steels, which include stainless steels and tool steels, are the most common manufacturing metals.

stiff

Not having the ability to return to an original state once having been deformed. Stiff materials show a steep modulus on the stress-strain curve.

strength

A general measure of how well a material withstands various mechanical forces. Types of strength include tensile, yield, and impact.

strength-to-weight ratio

The relationship between a material's strength and its weight. Materials with a high strength-to-weight ratio are light but also very strong.

stress

A force that attempts to deform an object. Stress includes compressive, shear, and tensile stress.

superalloys

An expensive, complex metal alloy designed to perform under intense conditions, such as elevated temperatures. Superalloys are also known as high performance alloys.

surface porosity

The number of small spaces or voids within the surface of a solid material. Surface porosity can lead to cracks and other defects in a metal part.

synthetic polymers

A polymer that is chemically manufactured. Synthetic polymers include many different types of plastic.

tantalum

A very hard, ductile metal that is highly resistant to heat and corrosion. Tantalum is often added to superalloys and carbide cutting tools.

tempering

The heat treatment of metals to temperatures below the recrystallization phase, followed by gradual cooling. Tempering can increase a material's hardness.

tensile strength

A material's ability to resist forces that attempt to pull it apart. Tensile strength is the amount of tensile stress a material can withstand before fracturing.

tensile stress

A force that attempts to pull apart or stretch a material. Tensile stress is a type of mechanical force.

thermal conductivity

The ability of a material to act as a medium for conveying heat. Most metals usually have high thermal conductivity, while polymers often have low thermal conductivity.

thermal degradation

Deterioration of a material due to overexposure to heat or sun. Thermal degradation can accelerate oxidation in a plastic.

thermal expansion

The tendency of a material to increase in size as it increases in temperature. Every material has its own unique rate at which it expands when subjected to increases in temperature.

thermal stress

Damage to a material due to excessive or abrupt changes in temperature. Thermal stress can cause a material to warp or crack.

thermoplastics

A group of plastics that can be repeatedly heated, cooled, and shaped. Thermoplastics consist of molecule chains that are not cross-linked.

thermoset

A group of plastics that are permanently hardened by heating. Thermosets, also known as thermosetting plastics, have covalent bonds and cross-linked molecule chains.

three-dimensional

3D. Having a length, depth, and width. Three-dimensional parts are created during additive manufacturing processes.

tin

A nonferrous metal that is very soft. Tin is weak in its pure state but is stronger when alloyed with copper to make bronze.

titanium

A nonferrous metal that is silver-gray. Titanium has a high strength-to-weight ratio, excellent flexibility, and exceptional corrosion resistance.

titanium alloys

A metal containing titanium, which is a silver-gray, strong, and lightweight metal known for its corrosion resistance. Titanium alloys, which are often biocompatible, are frequently used in medical applications.

titanium-aluminum-vanadium alloys

A metal containing larger amounts of titanium, aluminum, and vanadium along with various, lesser amounts of other alloying elements. Titanium-aluminum-vanadium alloys are common types of titanium alloys used in additive manufacturing processes.

tool steels

A grouping of steels designed to be used as cutting tools, dies, punches, and other tools. Tool steels are designed for toughness, hardness, and wear resistance.

tooling

Assorted tools used in various manufacturing processes. Tooling that can be created by additive manufacturing processes include molds, assembly fixtures, and medical guides.

toughness

A material's ability to absorb mechanical forces before it breaks. Toughness includes specific categories such as impact toughness.

traditional manufacturing

A manufacturing process that involves creating a part by shaping or removing material from a workpiece. Traditional manufacturing operations include metal cutting and forming.

transparency

The degree to which a material allows light to pass through it. Transparency is an optical property present in many polymers.

transparent

Having the quality of allowing light to pass through. Transparent objects can be seen through.

ultrasonic consolidation

UC. A sheet lamination process that uses high-frequency vibrations to bond successive layers of material together to build a final part. Ultrasonic consolidation most frequently uses sheets of metal foil or tape as build material.

ultraviolet degradation

UV degradation. The deterioration of a material due to overexposure to the ultraviolet radiation in sunlight. Ultraviolet degradation is typically associated with plastics.

ultraviolet radiation

UV radiation. Energy transmitted as invisible wavelengths. Ultraviolet radiation is used in the curing process for some thermosets.

ultraviolet rays

UV rays. Potentially harmful wavelengths from the sun that are invisible to the naked eye. Ultraviolet rays can damage a plastic at the molecular level.

ultraviolet-curable

UV-curable. Able to be hardened through exposure to ultraviolet light. Ultraviolet-curable materials include a variety of photopolymers.

uniform

To be constant and unchanging. Uniform crystal structures compose all metals.

vat photopolymerization

An additive manufacturing (AM) method that builds a part by curing layers of photopolymer with light. Vat photopolymerization processes include stereolithography (SLA) and digital light processing (DLP).

vertically

Perpendicular to the horizon or ground. Vertically oriented objects span up and down.

viscoelastic

Having both elastic and viscous properties. Viscoelastic materials can return to their original shape after undergoing stress, but they will lose shape over time.

viscosity

A material's resistance to flow. Viscosity is often affected by temperature.

viscous

Having a high resistance to flow. Viscous fluids tend to be sticky or syrupy.

warp

To physically twist or deform. Warping is often a result of internal stress within a material.

water atomization

An atomization process that creates powder by breaking up liquid into droplets using high-pressure water. Water atomization produces irregularly shaped and sized powder particles.

wear resistance

A material's ability to resist the gradual wearing away caused by abrasion and friction. Increased wear resistance can lengthen the life of a material.

weight

The force of a mass due to gravity. Without gravity, objects have no weight.

whiskers

A short, thin filament used for composite reinforcements. Whiskers are smaller than fibers but larger than particles.

X axis

An imaginary line that runs parallel to the horizon. X axes usually run left to right.

Y axis

An imaginary line that runs parallel to the horizon. Y axes usually run back and forth.

yield strength

The maximum amount of stress a material can withstand before being permanently deformed. Yield strength is sometimes called a material's elastic limit.

Z axis

An imaginary line that runs perpendicular to the horizon. Z axes usually run up and down.

zinc

A bluish-white metal that is corrosion-resistant and has a relatively low melting point. Zinc is often alloyed with aluminum.